Gas separating unit and method for manufacturing the same

ABSTRACT

A method for manufacturing a gas separating unit which comprises laminating a metal plate on a material capable of separating a hydrogen gas (palladium alloy foil) by cladding, etching selectively a central portion of a cut clad plate (K) using an etching solution, to thereby expose an underlying palladium alloy foil layer, and providing a metal supporting plate on the other side of the palladium alloy foil layer. The method allows the manufacture of a gas separating unit having an enhanced effective area of a material capable of separating a hydrogen gas and is excellent in the handlability of a material capable of separating a hydrogen gas during manufacturing.

TECHNICAL FIELD

The present invention relates to a gas separating unit that separates aparticular gas (for instance, hydrogen gas) in a mixed gas and a methodfor manufacturing the same.

BACKGROUND ART

So far, as a method of refining and recovering a hydrogen gas from ahydrogen-containing gas, there are methods such as a method in whichimpurities are separated and removed by use of a pressure swingabsorption method (PSA method) that makes use of an absorbing agent anda method for separating hydrogen by use of an organic or inorganichydrogen separating membrane. The method that uses a hydrogen separatingmembrane is gathering attention in view of energy saving, separationefficiency, simplicity of apparatus configuration, easiness in operationand so on.

As the hydrogen separating membrane, membranes of organic polymers suchas polyimide, polysulfone and so on; porous membranes of inorganicmaterials such as porous glass, porous ceramics and so on; and membranesof palladium or palladium alloys can be cited. For instance, inJP-A-07-124453, steps of forming a hydrogen separating membrane aredescribed, in which on one surface of a metal support thin films ofpalladium and other metal, respectively, are alternately deposited bymeans of electroplating, on one surface of the metal support a lot offine holes are bored by means of etching, heat treatment is applied toform a palladium alloy, furthermore a surface of a metal plate is etchedto form a lot of fine holes, and these are integrated to form a hydrogenseparating membrane.

However, there are problems in that it is difficult to form a platinglayer excellent in the adherence directly on a metal support plate suchas a stainless steel sheet and so on as mentioned above; and an alloylayer of palladium and nickel in the lastly applied heat treatment stepmay not be stably formed with a definite thickness.

Furthermore, there is another problem in that since in the plating,defects such as pinholes and so on are likely to occur, thin films ofmetal such as palladium and so on are formed with pores. In particular,in the case of multi-layered plating being applied, since the conditionssuch as a plating bath composition, an electric current, a temperatureand so on have to be strictly controlled; that is, it becomes a verycumbersome process.

Still furthermore, there is still another problem in that since anexposed area of a thin film of metal such as palladium and so on cannotbe made larger, there is a limit in an amount of permeable gas.

An object of the present invention is to provide a gas separating unitin which, in separating hydrogen gas, an effective area of a materialcapable of separating a hydrogen gas can be made larger and a method formanufacturing the same.

Furthermore, another object of the invention is to provide a method formanufacturing a gas separating unit that takes the handlability of amaterial capable of separating a hydrogen gas into consideration.

Still furthermore, still another object of the invention is to provide agas separating unit that can increase an exposed area of a materialcapable of separating a hydrogen gas and can increase an amount ofpermeable hydrogen gas.

DISCLOSURE OF INVENTION

A gas separating unit according to the present invention ischaracterized in that a material capable of separating a hydrogen gashas an extension frame that extends the foil laminated on one surfacethereof and a metal support body that supports the foil and has a lot ofholes laminated on the other surface thereof.

Furthermore, a gas separating unit according to the invention ischaracterized in that a laminated plate is formed by laminating amaterial capable of separating a gas on one surface of a metal plate,after an obtained laminated plate is made thinner in its thickness, themetal plate of the laminated plate is etched to expose the materialcapable of separating a gas and an extending frame is formed.

In these gas separating units, the material capable of separating ahydrogen gas or the material capable of separating a gas is preferableto be a palladium foil or a palladium alloy foil.

A method of manufacturing a gas separating unit according to theinvention is characterized in that on one surface of a metal plate amaterial capable of separating a hydrogen gas is laminated by a claddingprocess to manufacture a clad plate; an obtained clad plate is cut intoa cut clad plate; the metal plate of the cut clad plate is etched toexpose the material capable of separating a hydrogen gas and anextending frame is formed, and on the other surface of the material ametal support that supports the material is laminated.

Furthermore, a method of manufacturing a gas separating unit accordingto the invention is characterized in that on one surface of a metalplate a material capable of separating a gas is laminated to form alaminated plate; and, after an obtained laminated plate is made thinnerin its thickness, the metal plate of the laminated plate is etched toexpose the material capable of separating a gas and an extending frameis formed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view for explaining a structure of agas separating unit.

FIG. 2 is a schematic diagram of a clad plate-processing device thatpartially shows manufacturing steps of a gas separating unit.

FIGS. 3( a) through 3(c) are diagrams for explaining the etching of acut clad plate K.

FIG. 4 is an explanatory diagram showing an example of a method ofseparating hydrogen by use of a hydrogen gas separating unit.

FIG. 5 is schematic perspective view of a hydrogen gas separator Y.

BEST MODE FOR CARRYING OUT THE INVENTION

In what follows, a hydrogen gas separating unit according to the presentinvention will be explained with reference to the drawings.

FIG. 1 is a perspective view in which in order to explain a structure ofa hydrogen gas separating unit A, it is exploded in three layers offirst, second and third layers.

In FIG. 1, in the hydrogen gas separating unit A, on one surface of amaterial 13 capable of separating a hydrogen gas (for instance, apalladium alloy foil; in the following explanation, the palladium alloyfoil will be taken as an example) an extending frame 10 is laminated,and on the other surface thereof, a metal support 11 provided with a lotof holes is laminated.

As shown in FIG. 1, the extending frame 10 that is laminated on a topsurface of the hydrogen gas separating unit A is a frame body having ina center portion thereof two openings 105 formed by etching and so on.As a shape of the openings 105, various shapes such as square, hexagon,circle, ellipse and so on can be applied. A way of arrangement thereofis neither restricted to a particular one. The extending frame 10, whenopened as large as possible, is preferable because a gas permeation areacan be made larger. It may be preferably formed in a structure with, forinstance, a periphery portion 101 alone.

Furthermore, in taking the damage during handling of the palladium alloyfoil 13 into consideration, as shown in FIG. 1, a center portion 102maybe preferably formed. As a material of the extending frame 10,stainless steel, nickel or nickel base alloy, copper or copper alloy,iron alloy and so on can be preferably cited. A thickness of theextending frame 10 is preferably in the range of 10 to 500 μm and morepreferably in the range of substantially 50 to 200 μm. When thethickness thereof is less than 10 μm, the mechanical strength isdeficient as the frame body; on the other hand, when the thicknessexceeds 500 μm, it unfavorably takes a long time to form by means of,for instance, etching and so on.

In the next place, the metal support 11 that is laminated on the othersurface of the palladium alloy foil 13 will be explained.

In the metal support 11, circular or elliptic fine holes b having adiameter in the range of 10 to 500 μm, and preferably in the range of 50to 200 μm are formed. When the diameter is less than 10 μm, theventilation resistance of gas is large; on the other hand, when itexceeds 500 μm, the palladium alloy foil 13 bites in the fine holes band cracks tend to be caused in the palladium alloy foil 13. A formationdensity of the fine holes b is preferably in the range of substantially150 to 3000 holes/cm².

Furthermore, a shape of the fine holes b, as shown in FIG. 1, may be along hole shape in which one diameter is very long. A state ofarrangement of the fine holes b, though may be arranged in any way, whenarranged in a staggered way, is preferable because a hole formationdensity can be heightened.

The metal support 11 is preferably a metal plate such as a stainlesssteel plate, nickel or nickel alloy plate, copper or copper alloy plate,iron alloy plate and so on. For the metal support 11, as a material,porous inorganic materials such as ceramics and so on also can be used.

A thickness of the metal support 11 is preferably in the range of 10 to500 μm and more preferably in the range of substantially 50 to 200 μm.When the thickness is less than 10 μm, the mechanical strength as thesupport is deficient; on the other hand, when the thickness exceeds 500μm, it unfavorably takes a long time to form fine holes by means of, forinstance, etching and so on.

Subsequently, the palladium alloy foil 13 will be explained. Thepalladium alloy foil 13 is a thin foil of an alloy mainly made ofpalladium, one in which, alloyed to palladium, at least one kind ofother metal selected from elements (for instance, cobalt and nickel), IBgroup elements (for instance, copper, silver and gold) and IIIB groupelements (for instance yttrium) in the periodic table is preferablyused. Among these, an alloy foil of palladium and silver, and an alloyfoil of palladium, silver and holmium are more preferable.

A content of an element that is alloyed with palladium is preferably inthe range of 1 to 50% by weight and more preferably in the range of 10to 30% by weight. The reason to use the palladium alloy is becausesimple palladium causes hydrogen embrittlement and, when a content of analloying metal is made 1% by weight or more, the hydrogen embrittlementcan be inhibited from occurring.

Furthermore, when the content of the alloying metal exceeds 50% byweight, the permeation speed of hydrogen is unfavorably retarded.

A thickness of the palladium alloy foil 13, in view of the handlabilitythereof and so on, is preferably in the range of 3 to 100 μm and morepreferably in the range of 5 to 50 μm. When the thickness of thepalladium alloy foil 13 is less than 3 μm, pinholes are likely to beformed in the palladium alloy foil 13, resulting in deteriorating thepurity of separated hydrogen. On the other hand, when the thicknessexceeds 100 μm, the permeation speed of hydrogen becomes slow.

As materials capable of separating a hydrogen gas, the palladium alloyfoil was explained as an example; however, other materials also can beused as far as these can separate a hydrogen gas or other gas. A formthereof may be various such as plate-like, foil-like and so on. Here,“being capable of separating a gas” means a function capable ofselectively separating a particular gas from a mixed gas containing theparticular gas. The particular gas may be a hydrogen gas.

In the next place, a manufacturing method of a gas separating unitaccording to the invention will be explained.

FIG. 2 is a schematic diagram of a clad plate processing device whichshows part of manufacturing steps of a gas separating unit. Firstly, onone surface of a metal plate 21 that becomes an extending frame, apalladium alloy foil 23 is laminated according to the cladding process.In applying the cladding process, the metal plate 21 that is surfacecleaned in advance is wound around an unwinding reel 22 of the cladplate processing device shown in FIG. 2.

A thickness of the metal plate 21, counting on a decrease in thethickness at the following reel, is preferably in the range of 20 to 100μm.

Similarly, a palladium alloy foil 23 that is surface cleaned in advanceis wound around an unwinding reel 24.

As the palladium foil, one that has a thickness in the range of 6 to 100μm that is thicker than the aforementioned finish thickness can be used.The use of a thicker one allows easily performing the handling at thecladding.

The metal plate 21 and the palladium alloy foil 23 are simultaneouslyunwound from the unwinding reels 22 and 24 and wound around electroderolls 26 and 26 protruded into an etching chamber 25, and in the etchingchamber 25 the respective laminate surfaces are sputter etched toactivate.

A method of applying the sputter etching to activate, as previouslydisclosed by the present inventors in JP-A-01-224184, is preferablyperformed (1) in a very low pressure inert gas atmosphere in the rangeof 1×10⁻¹ to 1×10⁻⁴ Torr, (2) by performing glow discharge by applyingan alternate current in the range of 1 to 50 MHz between one electrodein which each of the metal plate 21 and the palladium alloy foil 23 isgrounded and insulatively supported other electrode, (3) and with anelectrode area exposed in a plasma generated by the glow discharge atone third or less of an electrode area, (4) by applying the sputteretching. Thereafter, by use of a rolling unit 27 disposed in a vacuumtank 20, a cladding process (cold welding with pressure) is applied, aclad plate 29 having a two-layered structure is wound with a windingroll 28, and thereby a clad plate 29 having the two layered laminatedstructure is manufactured. The clad plate 29 may be rolled in a rollingstep as shown below.

Rolling Step (Reroll)

The clad plate 29 is again rolled to reduce both thicknesses of themetal plate 21 and the palladium alloy foil 23 to make thinner. Arolling reduction is preferably in the range of 20 to 70%. When it isless than 20%, thinning of the palladium alloy foil 23 is not caused inthe rolling process; on the other hand, when it exceeds 70%, since awavy undulation is formed at a bonded interface of the clad plate at therolling, a thickness of the foil becomes uneven, resulting indeteriorating in the strength as a whole film. For instance, when one inwhich a silver/palladium alloy foil having an initial thickness of 20 μmand a stainless plate having an initial thickness of 200 μm arelaminated according to the cladding process is rolled at the rollingreduction of 50%, one in which the respective thicknesses are reduced by50% is obtained.

The rolling process may be performed in vacuum; however, one that waslaminated, even when rolled in air, does not at all deteriorate in thebonding strength.

Thus-manufactured clad plate 29 is cut in appropriate sizes of lengthand width to form a cut clad plate K (FIG. 3( a)), and the cut cladplate K is supplied as an original plate of a hydrogen gas separatingunit.

In the next place, on one surface of the cut clad plate K obtained inthe previous step, an opening 105 is formed by means of etching. As amethod of applying etching, firstly, on one surface (metal plate 21) ofthe cut clad plate K, a negative resist 31 is coated (FIG. 3( b)), afterbaking, through a mask thereon a pattern corresponding to the opening105 is formed, light such as ultraviolet light or the like is irradiatedto expose. After the exposure, development is applied (refer to FIG. 3(c)) followed by post-baking further followed by etching to removeremaining resist, and thereby an extending frame 10 is completed.

In order to improve the resist adherence on the metal plate 21, it ispreferable to cleanse a resist coating surface by, as pretreatment,applying alkali washing to the cut clad plate K with an aqueous solutionof sodium hydroxide followed by water washing, neutralizing and drying.As a type of the resist, a water-soluble type such as casein type, PVAtype and so on and a solvent-soluble type such as acrylic polymer systemare used. As the resist coating conditions, for instance, ones such asmentioned below are preferable.

Kind of resist; water-soluble PVA-dichromate system [FR-14 manufacturedby Fuji Yakuhin Kogyo]

Thickness of coating; 7 μm.

As a method of coating a resist on a cleansed metal plate 21, roll coatmethod, spin coat method, dip drawing-up coat method and so on can beapplied.

A thickness of coating, though varying depending on the viscosity ofresist, pulling up speed and so on, from a viewpoint of resolution, ispreferably in the range of 3 to 15 μm. Subsequently, on a coating of theresist 31 a film mask on which a pattern image is formed in advance isbrought into intimate contact followed by irradiating UV light forsubstantially 60 to 70 sec.

In the subsequent development step, the resist in an unexposed portionis dissolved and removed to expose a surface of the metal plate 21, andthe exposed portion is etched in a later step (FIG. 3( c)). Thedevelopment is carried out by spray coating water. The coating of resist31 thereon a pattern that becomes the opening 105 is formed, prior tothe etching, in order to improve the adherence of the coating, ispreferably subjected to the post baking by use of hot air, farultraviolet radiation and so on. Ordinarily, it is applied at atemperature in the range of 100 to 120 degree centigrade for 15 to 30min.

The etching of the metal plate 21 is carried out in two steps.

Firstly, as a first step of the etching, an aqueous solution of 45 to49° Be (Baume) of ferric chloride is preferably sprayed on a surface ofa target. A liquid temperature of the aqueous solution of ferricchloride is preferably in the range of 45 to 65 degree centigrade. Inthe first etching, substantially 80 to 90% of an amount of total etchingis performed. In the next place, the second step of the etching iscarried out. In the second etching, in order to completely remove aremaining metal plate 21, electrolytic etching is applied. As anelectrolytic etching solution, a phosphoric acid solution is preferablyused; however, as far as a solution can etch the metal plate, a kindthereof is not particularly restricted. The etched metal plate 21 iswater washed to remove the resist, and thereby a framed palladium alloyfoil p that is part of the hydrogen gas separating unit A and in whichthe extending frame 10 and the palladium alloy foil 13 are integrated isobtained.

In the etching according to the present embodiment, an etching solutionwas sprayed from one surface side so that an area of the opening 105 ofthe metal plate might be 70 mm×140 mm. The removal of the resist wascarried out by immersing in an aqueous solution of 5 to 10% by weight ofsodium hydroxide heated to a temperature in the range of 50 to 70 degreecentigrade. In the embodiment, as a method of manufacturing a laminatedbody in which the metal plate 21 and the palladium alloy foil 23 areintegrated, the cladding method is used to explain; however, by means ofother method, both can be laminated. For instance, by use of anadhesive, a laminated body in which a metal plate 21 and a palladiumalloy foil 23 are integrated can be also manufactured.

Furthermore, a frame body may be formed by previously punching a centerpart of a metal plate by means of a press process or the like, and theframe body can be integrated with a palladium alloy foil by use of thewelding process.

Subsequently, on a lower side of the palladium alloy foil p that ismanufactured in the previous step and has a frame, a metal support plate11 such as shown in FIG. 1 is applied, and thereby a hydrogen gasseparating unit A according to the invention is brought to completion.Thus completed hydrogen gas separating unit A is fixed at the peripherythereof to a case 34 by means of laser welding and so on with a surfaceof the metal support plate 11 located inside thereof, and thereby ahydrogen gas separator Y is obtained (FIG. 5).

In the next place, an example of a method of separating hydrogen by useof the hydrogen gas separating unit A according to the invention will beexplained with reference to FIG. 4. As shown in FIG. 4, as a hydrogengas separating machine X, a hydrogen gas separating machine X in whichthe hydrogen gas separating unit A according to the invention isassembled is disposed.

When a raw material gas is introduced from a raw material gasintroducing pipe 42 at an upper portion of the hydrogen gas separatingmachine X, hydrogen gas in the raw material has goes through thepalladium alloy foil 13 of the hydrogen gas separating unit 105 and istaken out of a separated gas exhaust pipe 41 disposed at a lower portionas a permeated gas. On the other hand, a non-permeated gas is exhaustedoutside from an upper portion 43 of the hydrogen gas separating machineX.

INDUSTRIAL APPLICABILITY

A gas separating unit according to the present invention is large in anexposed area of a material capable of separating a hydrogen gas(palladium alloy foil) and a palladium alloy foil is in a state extendedwith an extending frame; accordingly, a gas separating unit can bemanufactured without destroying the palladium alloy foil. Furthermore,on a bottom side of the palladium alloy foil, a metal support plate isapplied; accordingly, the palladium alloy foil is not destroyed owing toa pressure of a raw material gas.

1. A method of manufacturing a gas separating unit characterized byincluding manufacturing a clad plate by laminating a material capable ofseparating a hydrogen gas on one surface of a metal plate by coldwelding after applying sputter etching; cutting the obtained clad plateto make a cut clad plate; etching the metal plate of the cut clad plateto expose the material capable of separating a hydrogen gas and formingan extension frame; and laminating on the other surface of the materiala metal support body that supports the material.
 2. The method of claim1 wherein said material capable separating a hydrogen gas is a palladiumfoil or a palladium alloy foil.
 3. A method of manufacturing a gasseparating unit characterized in including laminating a material capableof separating a gas on one surface of a metal plate to form a laminatedplate; thinning the obtained laminated plate by cold rolling to providea reduction of 20% to 70%; and etching the metal plate of the laminatedplate to expose the material capable of separating a gas and forming anextension frame.
 4. The method of claim 3 wherein said material capableseparating a hydrogen gas is a palladium foil or a palladium alloy foil.5. A method of manufacturing a gas separating unit, comprising providinga palladium alloy foil (13) consisting essentially of palladium and10–30% by weight of an alloying metal selected from the group consistingof cobalt, nickel, copper, silver, gold, holmium and mixtures thereof;providing a metal sheet (21) for lamination to said palladium alloy foil(13); subjecting at least one surface of said palladium alloy foil (13)and at least one surface of said metal sheet (21) to sputter etching toprovide sputter etched surfaces; bringing sputter etched surfaces ofsaid metal sheet (21) and said palladium alloy foil (13) together andcold welding together said palladium alloy foil (13) and said metalsheet (21) with pressure to provide a clad plate (K) laminatedstructure; subjecting said metal plate (21), having a thickness of10–500 μm, of said clad plate (K) laminate structure to etching so as toprovide a frame (10) comprising a peripheral portion (101), said frame(10) being substantially open in area surrounded by said peripheralportion (101); providing a support plate (11) of metal or ceramic andhaving a thickness of 10–500 μm, said support plate (11) having aplurality of fine openings B extending therethrough, said fine openingseach having a size of 10–500 μm, the number of said fine openings persquare centimeter being substantially 150–3,000; and laminating saidsupport plate (11) to a surface of said palladium alloy foil (13)opposite from said frame (10), said palladium alloy foil (13) having athickness of 5–50 μm.
 6. The method of claim 5, wherein said supportplate has a thickness of 50–200 μm.
 7. The method of claim 5, whereinsaid frame (10) has a thickness of 50–200 μm.
 8. The method of claim 5,wherein said palladium alloy foil (13) has a thickness of 5–50 μm. 9.The method of claim 5, wherein, following of said cold welding withpressure of said palladium alloy foil (13) to said metal sheet (21), theresultant laminate is re-rolled to provide a rolling reduction in therange of 20–70%.